The present invention relates in general to unrolling devices for rolls of a web-like material fed to high-speed processing machines, such as for example paper rolls for web fed rotary printing machines; in particularly, the invention relates to a method of and a device for the exchange of the rolls of the web-like material during the operation of the unrolling device.
From the German published patent application No. 2 619 236 a method for controlling the exchange of web rolls in the course of their unrolling process is devised according to which the swinging of the roll supporting reel into an adhering position relative to the processed roll, the acceleration of the new roll and the adjustment of its circumferential speed to the discharging speed of the old web and the actuation of the adhering and severing devices takes place at definite continuously computed values of the diameter or of the circumferential speed of the old roll. The computation is based on a predetermined value for a desired final diameter of the residual part of the old roll, on a predetermined value for the desired length of the adhered web portions and on the predetermined or measured time constants of respective mechanical actuation members as well as on the actual value of the discharge speed and the rotary speed of the old roll.
This known method, however, has the disadvantage that the time necessary for measuring and computing the instantaneous values of the diameter or of the circumference of the web roll during its unwinding process produces delays which introduce inaccuracies into the controlling process. Moreover, the known method necessitates a preliminary computation of the final diameter of the residual old roll by taking into account the thickness of the processed web material provided when the residual material on the old reel is to be kept at minimum.